sends the signal
to the process group
for a list of signals.
sends the signal to the calling process's process group.
(POSIX says: If
is less than or equal to 1, the behavior is undefined.)
For a process to have permission to send a signal
it must either be privileged (under Linux: have the
capability), or the real or effective
user ID of the sending process must equal the real or
saved set-user-ID of the target process.
In the case of
it suffices when the sending and receiving
processes belong to the same session.
On success, zero is returned.
On error, -1 is returned, and
is set appropriately.
is not a valid signal number.
The process does not have permission to send the signal
to any of the target processes.
No process can be found in the process group specified by
The process group was given as 0 but the sending process does not
have a process group.
SVr4, 4.4BSD (the
function call first appeared in 4BSD), POSIX.1-2001.
There are various differences between the permission checking
in BSD-type systems and System V-type systems.
See the POSIX rationale for
A difference not mentioned by POSIX concerns the return
BSD documents that no signal is sent and
returned when the permission check failed for at least one target process,
while POSIX documents
only when the permission check failed for all target processes.
is implemented as a library function that makes the call